1. Technical Field
The present invention relates to a printing method for use for image printing by ink droplet discharge as printing by inkjet printers, a printing device using the printing method, a printing program for exercising control over a printing operation of the printing device, and a computer-readable recording medium recorded with the printing program. The invention also relates to a printing device, program, and method, a printing data generation device, program, and method, all of which are suitable for a so-called inkjet printing process of discharging liquid ink particles of a plurality of colors on a printing medium, or a so-called sublimation printing process of ink sublimation through heat application using a printing head to an ink ribbon coated with a solid ink for attachment to a printing medium.
2. Related Art
In a previous-type printing method, for pseudo representation of M tones (M≧3), e.g., M=64 (tones) using two tones (binary) of whether or not to discharge the ink droplets, the ink droplets are changed in amount for dot size change for printing to a printing medium, or a dot is formed by a plurality of ink droplets. In the following, such a printing method with a pseudo M-tone is referred to as “pseudo multi-tone printing method”.
In Patent Document 1 of a previous printing method associated with the pseudo multi-tone printing method (JP-A-2002-361909), for the aim of achieving even consistency between any two dots discharged on a printing medium, i.e., for making the granularity better, a smaller ink droplet, i.e., smaller dot, is discharged between the two dots for compliment use. In this method, a plurality of nozzles are disposed in several lines along a sub-scanning direction, and these nozzles discharge ink droplets for printing. In this configuration, the nozzles may be displaced in a main scanning direction, and the dot-to-dot distance may thus become uneven, i.e., a banding problem occurs. For taking measures against such a banding problem, the ink droplets are increased in amount to make the dots larger, which are originally formed with a relatively wide dot-to-dot distance so that the uneven space becomes seemingly even.
In Patent Document 2 of another previous printing method associated with the pseudo multi-tone printing method (JP-A-6-191040), when a printing image is of a photo, the image is printed with smaller dots for the aim of reproducing the photo with high resolution. When a printing image is of letters and characters, the image is printed with larger dots for the aim of reproducing the letters and characters clearly, i.e., with clarity and high contrast.
The problem with such previous pseudo multi-tone printing methods of changing the dot size for pseudo representation of M tones (M≧3) is that it takes quite a long time due to the complexity of image processing. This thus results in the difficulty of changing the dot size in practical use.